As the computer turns on, repeatedly tap the BIOS/UEFI key. This is usually F2, F12, Del, or Esc. Navigate to the Boot tab using your keyboard.
In the end, you sit back, watch the “Getting files ready for installation” screen, and realize: an old external hard drive just saved you from hunting for a DVD or an 8 GB flash drive.
You install Windows normally, choosing the internal drive (or even another external drive if you want a portable Windows). The external installation drive stays untouched unless you deliberately format it. install windows from external hard drive
You plug the external drive into the target computer, restart, and enter the boot menu (usually F12, ESC, or F2). You select “USB Hard Drive” or the external drive’s name. The computer boots straight into the blue Windows Setup screen — just as if you were using a USB flash drive.
Select Custom: Install Windows only (advanced) for a clean installation. Choose the partition where you want to install Windows. As the computer turns on, repeatedly tap the BIOS/UEFI key
Installing Windows from an external hard drive is a practical way to bypass the storage limits of standard thumb drives or to keep a high-speed recovery tool ready at all times. While the process is similar to using a USB stick, there are specific steps you must follow to ensure your computer recognizes the external drive as a bootable device. Preparing Your Hardware
You open Command Prompt as Administrator . In the end, you sit back, watch the
Then you use bootsect /nt60 F: (where F: is your external drive) to write the Windows boot code onto it.